The cardia is also the site of the lower esophageal sphincter (LES)[7][8][9] (also termed cardiac sphincter[10], gastroesophageal sphincter[11], and esophageal sphincter[12]).

Nomenclature and classification

There is disagreement in the academic anatomy community over whether the cardia is part of the stomach, part of the esophagus or a distinct entity, as described in this article. The difference is more than semantic when used in clinical studies and applied to individual patients.

Classical anatomy textbooks, and some other resources[13][14], describe the cardia as the first of 4 regions of the stomach. This makes sense histologically because the mucosa of the cardia is the same as that of the stomach.

Many recent writings describe it as the LES.

Function

The stomach generates strong acids and enzymes to aid in food digestion. This digestive mixture is called gastric juice. The inner lining of the stomach has several mechanisms to resist the effect of gastric juice on itself, but the mucosa of the esophagus does not. The esophagus is normally protected from these acids by a one-way valve mechanism at its junction with the stomach. This one-way valve is called the lower esophageal sphincter (LES), and prevents gastric juice from flowing back into the esophagus.